Phenylalanine Effects on Brain Function in Adult Phenylketonuria.

OBJECTIVE: To evaluate the relationship between circulating phenylalanine and brain function as well as neuropsychiatric symptoms in adults with phenylketonuria. METHODS: In this prospective cross-sectional study, early-treated patients with phenylketonuria older than 30 years and age- and sex-matched controls were included. Extensive neurologic evaluation, neuropsychological and behavioral testing, sensory and motor evoked potentials, and MRI were performed. CSF concentrations of neurodegenerative markers were evaluated in addition in a subset of 10 patients. RESULTS: Nineteen patients with phenylketonuria (median age 41 years) with different phenylalanine levels (median 873 µmol/L) entered the study. They showed higher prevalence of neurologic symptoms, cognitive and behavioral abnormalities, autonomic dysfunction, alterations in neurophysiologic measures, and atrophy in putamen and right thalamus compared to controls. In CSF, patients with phenylketonuria exhibited higher ß-amyloid 1-42 (p = 0.003), total tau (p < 0.001), and phosphorylated tau (p = 0.032) levels compared to controls. Plasma phenylalanine levels highly correlated with the number of failed neuropsychological tests (r = 0.64, p = 0.003), neuropsychiatric symptoms (r = 0.73, p < 001), motor evoked potential latency (r = 0.48, p = 0.030), and parietal lobe atrophy. CONCLUSIONS: Our study provides strong evidence for a correlation between phenylalanine levels and clinical, neuropsychological, neurophysiologic, biochemical, and imaging alterations in adult patients with phenylketonuria.

The role of high-field magnetic resonance imaging in parkinsonian disorders: Pushing the boundaries forward.

Historically, magnetic resonance imaging (MRI) has contributed little to the study of Parkinson's disease (PD), but modern MRI approaches have unveiled several complementary markers that are useful for research and clinical applications. Iron- and neuromelanin-sensitive MRI detect qualitative changes in the substantia nigra. Quantitative MRI markers can be derived from diffusion weighted and iron-sensitive imaging or volumetry. Functional brain alterations at rest or during task performance have been captured with functional and arterial spin labeling perfusion MRI. These markers are useful for the diagnosis of PD and atypical parkinsonism, to track disease progression from the premotor stages of these diseases and to better understand the neurobiological basis of clinical deficits. A current research goal using MRI is to generate time-dependent models of the evolution of PD biomarkers that can help understand neurodegeneration and provide reliable markers for therapeutic trials. This article reviews recent advances in MRI biomarker research at high-field (3T) and ultra high field-imaging (7T) in PD and atypical parkinsonism. © 2017 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Time- and frequency-domain parameters of heart rate variability and sympathetic skin response in Parkinson's disease.

The autonomic nervous system (ANS) is regularly affected in Parkinson's disease (PD). Information on autonomic dysfunction can be derived from e.g. altered heart rate variability (HRV) and sympathetic skin response (SSR). Such parameters can be quantified easily and measured repeatedly which might be helpful for evaluating disease progression and therapeutic outcome. In this 2-center study, HRV and SSR of 45 PD patients and 26 controls were recorded. HRV was measured during supine metronomic breathing and analyzed in time- and frequency-domains. SSR was evoked by repetitive auditory stimulation. Various ANS parameters were compared (1) between patients and healthy controls, (2) to clinical scales (Unified Parkinson's disease rating scale, Mini-Mental State Examination, Becks Depression Inventory), and (3) to disease duration. Root mean square of successive differences (RMSSD) and low frequency/high frequency (LF/HF) ratio differed significantly between PD and controls. Both, HRV and SSR parameters showed low or no association with clinical scores. Time-domain parameters tended to be affected already at early PD stages but did not consistently change with longer disease duration. In contrast, frequency-domain parameters were not altered in early PD phases but tended to be lower (LF, LF/HF ratio), respectively higher (HF) with increasing disease duration. This report confirms previous results of altered ANS parameters in PD. In addition, it suggests that (1) these ANS parameters are not relevantly associated with motor, behavioral, and cognitive changes in PD, (2) time-domain parameters are useful for the assessment of early PD, and (3) frequency-domain parameters are more closely associated with disease duration.

Fluorodeoxyglucose positron emission tomography in Richardson's syndrome and progressive supranuclear palsy-parkinsonism.

BACKGROUND: We hypothesized that postural instability and cognitive decline in patients with Richardson's syndrome could be a consequence of reduced thalamic and frontal metabolism. Severe Parkinsonian signs in patients with progressive supranuclear palsy-parkinsonism may be reflected by alterations in putaminal metabolism. METHODS: Eleven patients with Richardson's syndrome, 8 patients with progressive supranuclear palsy-parkinsonism, 12 with Parkinson's disease, and 10 controls underwent clinical assessment and fluorodeoxyglucose positron emission tomography (PET). RESULTS: Richardson's syndrome patients showed pronounced thalamic hypometabolism, and patients with progressive supranuclear palsy-parkinsonism pronounced putaminal hypometabolism, compared to all other investigated groups. The putamen/thalamus uptake ratio differentiated progressive supranuclear palsy-parkinsonism from Richardson's syndrome (area under the curve 5 0.86) and from Parkinson's disease (area under the curve 5 0.80) with acceptable accuracy. Frontal hypometabolism was predominantly found in Richardson's syndrome patients. CONCLUSIONS: Richardson's syndrome, progressive supranuclear palsy-parkinsonism and Parkinson's disease showed different metabolic patterns in fluorodeoxyglucose PET.

Biomarker candidates of neurodegeneration in Parkinson's disease for the evaluation of disease-modifying therapeutics.

Reliable biomarkers that can be used for early diagnosis and tracking disease progression are the cornerstone of the development of disease-modifying treatments for Parkinson's disease (PD). The German Society of Experimental and Clinical Neurotherapeutics (GESENT) has convened a Working Group to review the current status of proposed biomarkers of neurodegeneration according to the following criteria and to develop a consensus statement on biomarker candidates for evaluation of disease-modifying therapeutics in PD. The criteria proposed are that the biomarker should be linked to fundamental features of PD neuropathology and mechanisms underlying neurodegeneration in PD, should be correlated to disease progression assessed by clinical rating scales, should monitor the actual disease status, should be pre-clinically validated, and confirmed by at least two independent studies conducted by qualified investigators with the results published in peer-reviewed journals. To date, available data have not yet revealed one reliable biomarker to detect early neurodegeneration in PD and to detect and monitor effects of drug candidates on the disease process, but some promising biomarker candidates, such as antibodies against neuromelanin, pathological forms of α-synuclein, DJ-1, and patterns of gene expression, metabolomic and protein profiling exist. Almost all of the biomarker candidates were not investigated in relation to effects of treatment, validated in experimental models of PD and confirmed in independent studies.

Transcranial sonography reveals cerebellar, nigral, and forebrain abnormalities in Friedreich's ataxia.

BACKGROUND: Friedreich's ataxia (FA) is essentially characterized by degeneration of the dorsal root ganglia, the dorsal nuclei of Clarke, and the long spinal fiber tracts, yet there is accumulating evidence that neurodegeneration extends beyond these predilection sites. Transcranial sonography (TCS) has evolved as a valuable complementary neuroimaging tool in the assessment of neurodegenerative diseases due to its capacity to well depict structural changes and the accumulation of heavy metals. Its use for assessing cerebellar neurodegeneration, however, has not yet been investigated.Here we investigated whether TCS allows to assess particular features of cerebellar as well as midbrain and forebrain abnormalities in FA. METHODS: Comprehensive TCS imaging of 34 FA patients and 34 age-matched healthy controls. RESULTS: Hyperechogenicity of the dentate nucleus was very frequent in FA patients (85%) and could even be observed in patients with short disease duration, suggesting that dentate alterations are a common and probably early feature of FA. Substantia nigra was significantly hypoechogenic, possibly indicating regional changes in subcellular brain iron regulation. FA patients showed significantly enlarged 4th, 3rd, and lateral ventricles, thus corroborating earlier MRI and postmortem findings of substantial cerebellar and forebrain atrophy in FA. CONCLUSIONS: TCS provides a quick-to-apply and inexpensive in vivo assessment of both cerebellar and noncerebellar abnormalities in FA, in particular highlighting dentate hyperechogenicity as a core feature. It might serve as a promising tool for imaging aspects of cerebellar neurodegeneration also in other neurodegenerative disorders.

Hyperechogenicity of the substantia nigra: pitfalls in assessment and specificity for Parkinson's disease.

During the last decade, substantia nigra (SN) hyperechogenicity has been established as a valuable supplementary diagnostic marker for Parkinson's disease. As an increasing number of studies indicate that this ultrasound feature may even be evident before motor symptoms of Parkinson's disease occur, longitudinal studies revealing its value as a screening instrument for subjects at risk are awaited with great expectancy. At the same time, other studies have shown that SN hyperechogenicity is not only found in Parkinson's disease but also in other disease entities. Limitations and pitfalls of the method need to be considered to evaluate and compare these studies. Taking these into account, it is important to realize that in some other neurodegenerative diseases as well as in disorders associated with an increased risk for Parkinson's disease hyperechogenicity can be found--usually, however, less prevalent. Interestingly, even in subgroups of patients with non-neurodegenerative disorders, SN hyperechogenicity can be detected. This holds, for example, true for multiple sclerosis patients with a higher rate of disease progression. In this disorder, microglia activation is known to occur, which is also evident in Parkinson's disease. This pathomechanism as well as increased iron content is known to contribute to SN hyperechogenicity. From the studies published so far it can be concluded that, although SN hyperechogenicity is not only found in Parkinson's disease, assessment of the echogenicity of the SN and other ultrasound features is valuable in the differential diagnosis of Parkinsonian syndromes and most probably in subjects at risk. Further elucidation of the cause of the echosignal will not only contribute to the understanding of the pathophysiology of some neurodegenerative diseases but also to an even better implementation in the clinical routine and for scientific studies.

Place value of transcranial sonography in early diagnosis of Parkinson's disease.

Transcranial B-mode sonography (TCS) is a relatively new method which has been proven to be helpful in the diagnosis of Parkinson's disease (PD). Due to the underlying physical principles, supplementary information to other neuroimaging methods can be derived. Substantia nigra (SN) hyperechogenicity is the characteristic feature of idiopathic PD, which can help in the differentiation of atypical parkinsonian syndromes like multiple system atrophy or progressive supranuclear palsy. Besides, the quick 'look into the brain' can easily visualize an enlargement of the ventricular system, alterations of the basal ganglia like increased contents of calcium or trace metals, or a missing brain stem raphe, typically seen in depressive disorders, and can therefore give further diagnostic hints for symptomatic parkinsonian syndromes. Many studies indicate that SN hyperechogenicity constitutes a stable marker, irrespective of the disease stage. In a prospective study of patients with very first signs of yet unclear parkinsonism, a high predictive value of TCS for the diagnosis of PD could be proven. Moreover, there is accumulating evidence that SN hyperechogenicity could play a role in the premotor diagnosis of PD. In this review, the additional diagnostic value of TCS in the early diagnosis of PD as well as limitations of the method are being discussed.

Progressive secondary neurodegeneration and microcalcification co-occur in osteopontin-deficient mice.

In the brain, osteopontin (OPN) may function in a variety of pathological conditions, including neurodegeneration, microcalcification, and inflammation. In this study, we addressed the role of OPN in primary and secondary neurodegeneration, microcalcification, and inflammation after an excitotoxic lesion by examining OPN knock-out (KO) mice. Two, four, and ten weeks after injection of the glutamate analogue ibotenate into the corticostriatal boundary, the brains of 12 mice per survival time and strain were evaluated. OPN was detectable in neuron-shaped cells, in microglia, and at the surface of dense calcium deposits. At this primary lesion site, although the glial reaction was attenuated in OPN-KO mice, lesion size and presence of microcalcification were comparable between OPN-KO and wild-type mice. In contrast, secondary neurodegeneration at the thalamus was more prominent in OPN-KO mice, and this difference increased over time. This was paralleled by a dramatic rise in the regional extent of dense microcalcification. Despite these differences, the numbers of glial cells did not significantly differ between the two strains. This study demonstrates for the first time a genetic model with co-occurrence of neurodegeneration and microcalcification, mediated by the lack of OPN, and suggests a basic involvement of OPN action in these conditions. In the case of secondary retrograde or transneuronal degeneration, OPN may have a protective role as intracellular actor.

Therapeutic strategies for Parkinson's disease based on data derived from genetic research.

Following the identification of mutations in alpha-synuclein as the cause of some rare forms of familial Parkinson's disease (PD), genetic research has uncovered numerous gene loci of PD. Meanwhile, several neurodegenerative diseases have been shown to accumulate a-synuclein in neuronal and glial cells summarizing this group of diseases as synucleinopathies. All currently known gene defects causing PD alter the ubiquitin-proteasomal pathway of protein degradation. Identification of these disease mutations allows studying the functional consequences which lead to cellular dysfunction and cell death in cell culture and transgenic animal models, to identify therapeutic targets and to test potential protective strategies in these models.